\begin{problem}{Jealous Numbers}{jealous.in}{jealous.out}{\timeLimit}

% Original idea : Andrew Stankevich
% Text          : Andrew Stankevich; light version by Dmitry Shtukenberg
% Tests         : Andrew Stankevich; light version by Dmitry Shtukenberg

\newcommand{\scdot}{\mathbin{\mkern-4mu\cdot\mkern-4mu}}

There is a trouble in Numberland, prime number $p$ is jealous of another prime number $q$.
She thinks that there are more integer numbers between $a$ and $b$, inclusively, that
are divisible by greater power of $q$ than that of $p$.
Help $p$ to get rid of her feelings. 

Let $\alpha(n, x)$ be maximal $k$ such that $n$ is
divisible by $x^k$. Let us say that a number $n$ is $p$-dominating over~$q$ if
$\alpha(n, p)>\alpha(n, q)$.
Find out for how many numbers between $a$ and $b$, inclusive
are $p$-dominating over~$q$.

\InputFile

The first line of the input file contains $a$, $b$, $p$ and $q$ 
($1 \le a \le b \le 10^{11}$; $10^3 \le p, q \le 10^6$; $p \ne q$; $p$ and $q$ are prime).

\OutputFile

Output one number --- how many numbers $n$ between $a$ and $b$, inclusive,
are $p$-dominating over $q$.

\Example
\begin{example}
\exmp{
1021108 1022117 1009 1013
}{
1
}%
\exmp{
1032334130 1032338170 1009 1013
}{
4
}%
\end{example}

\bigskip

In the first example only $1021108 = 1009 \scdot 1012$ is 1009-dominating over 1013.
The number $1022117 = 1009 \scdot 1013$ is within range but it is not 1009-dominating 
over 1013. 

In the second example there are 8 numbers divisible by 1009 or 1013
between 1032334130 and 1032338170: 1032334134, 1032335131, 1032335143, 1032336144,
1032336152, 1032337157, 1032337161 and 1032338170. Only 1032334134,
1032335143, 1032336152 and 1032337161 are 1009-dominating over 1013.

\end{problem}
